ProjectSummary Diseasemodelingwithpatient-derivedinducedpluripotentstemcells(iPSCs)enablesresearcherstoobserve theembryonicdevelopment,maturation,andagingofanycelltypefromthepatient?sbodyinalaboratorypetri dish.Thisnovelandpowerfultechnologythereforeenablesresearcherstocloselyobservethedevelopmentof age-related,lateonsetdiseasesthataffectspecificcellsinthepatientbyreplayingthemoleculareventsthat occurinsidethecellspriortoandduringthedisease.Withthisknowledgeinhand,researcherscanthen designtherapiesbasedonthemoleculardysfunctionsimplicatedincausingthedisease.Ahighlyactivearea ofdiseasemodelingresearchusingiPSCtechnologyisinAmyotrophicLateralSclerosis(ALS),adevastating neurodegenerativedisordercharacterizedbythedeathofmotorneurons,typicallyoccurringinlateadulthood, forwhichthereisnocureandpatientsfaceanaverageofthreeyearsofliferemaining.However,amajor challengecurrentlyfacingthisfieldisthatthemotorneuronsgrownfromiPSCsinthepetridisharemolecularly moresimilartoimmatureembryoniccellsratherthantomatureandagedadultcells.SinceALScausesthe deathofadultratherthanembryonicmotorneurons,anecessarygoalistogeneratematureandagedmotor neuronstostudyinthedish.Byintegratingcomparativegenomic,transcriptomic,andproteomicapproaches proposedinthisapplication,weaimtoidentifythemolecularroadblocksregulatingthepathtothemature motorneuronstate.First,wewillemployacomparativemedicineapproachbetweenmouseandhumancells tofindcommonanddistinctgenesandexpressionnetworksregulatingmotorneurondevelopment,maturation, aging,andALS-induceddegeneration.Thiscomparisonservestocaptureessentialmaturationandaging pathwaysinthemousethatcanhypotheticallybeenactedandacceleratedinhumancells.Second,wewill employasinglecellRNA-sequencingandproteomicapproachtodeeplyandsensitivelydetectpopulationsof maturemotorneuronsvulnerabletoALS.Lastly,wewillintegrateourdatatopredictandexperimentally validateregulatoryfactorscontrollingkeygeneexpressionnetworksiniPSC-derivedmotorneurons.By understandingthecellularsystemscontrollingthematurationandagingprocesses,wecanthendevelop strategiestoacceleratemotorneuronmaturationandaginginthedish,andtherebyfaithfullyreproducethe lateonsetmoleculareventsleadingtothedegenerationofmotorneuronsinALS.